1. Field of the Invention
This invention relates generally to a hydrocarbon conversion catalyst system and a process for reforming hydrocarbons in the presence of such catalyst system, and more particularly concerns a catalyst system comprising a first catalyst having a noble metal component and a second catalyst having a non-noble metal component and a crystalline aluminosilicate component, and a reforming process employing such catalyst system.
2. Description of the Prior Art
The catalytic reforming of hydrocarbon streams is one of the important hydrocarbon conversion processes that can be employed to provide high octane number hydrocarbon blending components for gasoline, as well as aromatics and liquefiable gases. The increasing demand for such materials makes desirable the development and use of improved reforming catalysts which result in enhanced production of high octane number gasoline blending components, light aromatics and liquefiable gases. Efforts to obtain enhanced production of higher octane number gasoline components using conventional platinum-on-alumina reforming catalysts generally result in excessive decrease in the yield of liquid reformate and in the production of increased amounts of non-liquefiable gases. Accordingly, there is a need for hydrocarbon conversion catalysts which are instrumental in producing a reformate having an improved octane value without also effecting an excessive decrease in the yield of liquid reformate and producing increased amounts of non-liquefiable gases.
Relevant hydrocarbon conversion catalyst comprising a physical mixture of components are disclosed in Kittrell, U.S. Pat. No. 3,535,231. The Kittrell patent discloses a process for the conversion of distillates and solvent-deasphalted residua employing a catalyst consisting of a physical mixture of particles of a first catalyst and of a second catalyst. The first catalyst comprises a layered clay-type crystalline aluminosilicate material and a component selected from rhenium and compounds of rhenium. The second catalyst comprises a layered clay-type crystalline aluminosilicate material, a component selected from Group VIII metals and compounds thereof, and a component selected from the group of silica-alumina gel, silica-alumina-titania gel, and silica-aluminazirconia gel. The mixtures are disclosed as being useful in hydrocracking, hydrodesulfurization, hydrodenitrification, hydrogenation, and hydroisomerization processes. However, Kittrell neither discloses nor suggests that his catalyst system would be useful in reforming operations. The layered clay-type crystalline aluminosilicates of Kittrell are in fact of insufficient pore size to be useful in reforming operations.
Relevant reforming catalysts are disclosed in Roberts et al., German Offenlegungsschrift No. P 2,627,822. The Roberts et al. German Offenlegungsschrift discloses a reforming catalyst comprising a mixture of platinum, palladium, iridium, rhodium, gallium, germanium or tin or compounds thereof, on a first solid support and a rhenium-containing component on a second solid support. However, unlike the present invention, this German application does not disclose the presence of a crystalline aluminosilicate component in the second solid support and the only solid supports disclosed are the inorganic oxides gamma-alumina and eta-alumina. In addition, the only benefit disclosed for the catalyst system of the German application is the maintenance of the yield of a higher octane reformate from the initial period of operation and through longer periods of operation by reducing hydrocracking reactions. Furthermore, relative to the case of the present invention, this benefit is achieved at relatively lower octane numbers and at relatively higher reforming temperatures and occurs primarily with feeds containing relatively high sulfur contents.
Copending patent application Ser. No. 86,707, of Pellet et al., filed Oct. 22, 1979 now U.S. Pat. No. 4,302,358, is directed to similar subject matter. Pellet et al. disclose that it is possible to improve the reforming activity of catalysts comprising a first compound comprising at least one Group VIII noble metal deposed on a solid catalyst support having acidic catalyst sites and a second component comprising rhenium or a compound thereof deposed on a solid catalyst support material. Pellet et al. point out that surprisingly, other things being equal, there is a substantial activity increase by thoroughly and intimately blending finely-divided particles of the first and second components to provide a thoroughly-blended composite and subsequently forming the composite into larger particles, in contrast to using only a particulate mixture of first and second catalyst components. The Pellet et al. catalysts have the additional advantage that they are even more effective in reforming high sulfur feeds than the catalysts of German Offenlegungsschrift No. P 2,627,822.
It is known that improved octane values can be obtained by employing novel catalysts in the tail reactor of a reforming operation. For example, each of Bertolacini et al., U.S. Pat. Nos. 3,772,183; 3,772,184; 3,798,154 and 4,134,823 discloses a reforming process which comprises contacting a novel catalyst composition disclosed therein with a hydrocarbon stream which had been partially reformed in the presence of a conventional reforming catalyst. However, none of these patents disclose the physical mixture of catalysts which is employed in the catalyst system of the present invention and which is essential to achieve the benefits as described hereinbelow of the present invention.